1. Field of the Invention
The invention relates to an electric power source system that has a plurality of electric power sources, and a method that controls an electric power source system.
2. Description of the Related Art
An electric power source control device that employs batteries of two different voltage systems is described in Japanese Patent Application Publication No. JP-A-2002-176704. In some cases, electric power source control devices that employ a plurality of electricity storage devices, including the electric power source control device described in JP-A-2002-176704, convert the voltage of a first electricity storage device to the voltage of a second electricity storage device via voltage converter, such as a DC/DC converter or the like and thereby charge the second electricity storage device or supply electric power to an electrical load whose direct power source is the second electricity storage device.
In the foregoing related-art technology that enables the bidirectional exchange of current between different voltage systems, however, when the voltage converter switches the direction of voltage conversion to the opposite direction, the supply of current is momentarily interrupted due to the time lag caused by the switching operation. Therefore, a system in which the interruption is avoided needs an effective measure to prevent the interruption.
In relation to this respect, JP-A-2002-176704 describes a condition for switching the voltage conversion direction, but does not disclose or indicate a measure as mentioned above.